Asthma in the U.S. and around the world has increased at an alarming rate over the last 20 years and currently affects more than 15 million Americans. There is some speculation as to the cause of this increase, whether due to more time spent indoors in “tighter” homes with less fresh air or because of improvements in early diagnosis of disease. A recent study concluded that the risk due to residential allergen and pollutant exposure accounted for 39% of doctor-diagnosed asthma in U.S. children less than 6 years old. 5,000,000 U.S. children (1 in 13) now suffer from asthma, accounting for 17% of all pediatric emergency room visits.
Allergic rhinitis or hay fever affects 40 million Americans. It can lead to rhinosinusitis (in 14% of the U.S. population) as well as otitis media (e.g. ear ache), the most common childhood disease requiring a healthcare visit.
In addition to the tremendous discomfort associated with these diseases and their all too often tragic outcomes (there are more than 5,000 asthma related deaths per year in the U.S.), the estimated annual cost of asthma in the U.S. is projected to be $14.5 billion this year, up from $6.2 billion only 10 years ago.
The first line of defense against these disease's symptoms recommended by allergists is to reduce environmental exposure. This can be accomplished by removing the allergen source (for example cats, cigarettes, molds, etc.), its reservoir (for example carpets, drapes, etc.) and also by cleaning the air through the use of high-efficiency air cleaners.
Existing air cleaner technology can be very effective at removing a high percentage of particles in the air stream passing through them by means of High Efficiency Particulate Air (HEPA) filters, electrostatic precipitators, etc.
The efficacy of these filters on the particle levels people actually breath, however, is directly dependent on the filter's efficiency, air changes per hour or airflow, and dynamics of the environment such as open doors or windows, forced air ventilation and particle sources within the room. Studies show that these variables, through mixing, can decrease a HEPA (typically 99.97% efficient) filters' effect on room particle counts to an average efficiency of 50% or less where the rooms' occupants are breathing.
As an example, people often utilize room air cleaner units in an attempt to achieve a reduction in particles levels within a localized area. These types of units effectively remove a high percentage of harmful particles from the air that flows through the unit. However, individuals within the area of the unit may not experience all of the beneficial results of this particle removal because the air that is discharged from the unit is able to pick up additional harmful particles from the surrounding environment prior to reaching and being breathed in by the individuals.